"I hoped that the outcome would be a conclusion with the arrival of a Turkish delegation to begin the accession conference later this afternoon, but that is by no means certain," he added.

Turkish Prime Minister Recep Tayyip Erdogan told Turkey's ruling AK party he would not compromise on the conditions for starting talks.

"We have protected and are continuing to protect our stance, which is appropriate to Turkey's national interests and political principles," he said, to loud applause.

The EU's member states must unanimously approve a negotiating mandate before talks with Turkey can begin.

At the centre of the crisis is Austria's insistence that the draft framework for entry talks should be rewritten, including the prospect of "privileged partnership", not just full membership, for Turkey.

Recent opinion polls suggest more than 70% of Austrians oppose full Turkish membership of the EU.

The predominantly Muslim country, with a population of 70 million, has had to meet strict criteria, including improving its shaky record on human rights, to begin accession talks.

Prime Minister Erdogan warned the EU must embrace its Muslim neighbour "or it will end up a Christian club".

His view was echoed by Mr Straw, who warned of a "theological-political divide, which could open up even further down the boundary between so-called Christian-heritage states and those of Islamic heritage".

If started, the Turkish negotiations are expected to take about 10 years.